A MEMS chip packaging structure

Abstract

The invention discloses a MEMS chip packaging structure, which belongs to the field of component packaging technology, and includes a ceramic box body and a metal cover plate; a nitrogen filling cavity is provided in the ceramic box body, a chip mounting area and a pad inner mounting area are provided on the bottom wall of the nitrogen filling cavity, and the MEMS chip is electrically connected to the internal pad; a pad outer mounting area and a circuit through hole are provided on the bottom wall of the ceramic box body; a heat dissipation cavity is provided in the side wall of the ceramic box body, a heat dissipation port and a plurality of heat conduction ports are provided on the heat dissipation cavity, and the plurality of heat conduction ports are arranged in sequence from bottom to top along the side wall of the nitrogen filling cavity, and a metal heat dissipation plate capable of closing the heat dissipation port is embedded in the heat dissipation cavity; an elastic heat sink is provided on the metal cover plate, a heat conduction block is provided on the elastic heat sink, and a thermal expansion and contraction part for connecting and disconnecting with the metal heat dissipation plate is provided on the heat conduction block, and the connection and disconnection spacing between the thermal expansion and contraction part of the heat conduction block and the metal heat dissipation plate increases step by step from bottom to top. The heat dissipation effect can be self-regulated according to temperature changes to meet different heat dissipation requirements.

Description

Technical Field

[0001] The present invention relates to the technical field of component packaging, and in particular to a MEMS chip packaging structure. Background Art

[0002] MEMS (Micro-Electro-Mechanical System), also known as micro-electro-mechanical system, is an emerging technology developed from traditional integrated circuit technology. It realizes sensing or execution functions by making micron-nanoscale mechanical structures. In order to protect the MEMS chip from external environmental interference factors, the MEMS chip generally needs to be packaged in a packaging structure. The packaging structure of traditional MEMS sensor chips mainly includes three types of packaging: metal material packaging, ceramic material packaging, and plastic material packaging. Among them, ceramic packaging is widely used due to its good thermal conductivity and good airtightness. For example, the patent number is "201510441724.4", and the patent name is "A packaging structure for a MEMS sensor", which includes: a silicon nitride ceramic base and a metal cover for fixing the MEMS sensor chip. An internal pad is welded on the upper surface of the silicon nitride ceramic base, and an external pad is welded on the lower surface of the silicon nitride ceramic base. The internal pad and the external pad are connected through an internal circuit. The metal cover is welded at the opening of the silicon nitride ceramic base. On the one hand, the low melting point of the metal cover is conducive to welding. On the other hand, it is conducive to timely exporting the heat generated by the MEMS sensor chip from the packaging structure to avoid affecting the temperature of the MEMS sensor chip. However, the above-mentioned packaging structure has a poor heat dissipation effect relying solely on the ceramic base and the metal cover. High temperature will reduce the working accuracy of the MEMS sensor chip. Summary of the invention

[0003] The purpose of the present invention is to solve the above technical problems and provide a MEMS chip packaging structure, the heat dissipation effect of which can be self-regulated according to temperature changes to meet different degrees of heat dissipation requirements.

[0004] To achieve the above-mentioned purpose, the present invention provides the following scheme: The present invention discloses a MEMS chip packaging structure, comprising a ceramic box body with a mounting port on the top and a metal cover plate for blocking the mounting port; a nitrogen filling cavity communicating with the mounting port is provided in the ceramic box body, a chip mounting area for fixing the MEMS chip and an inner pad mounting area for welding an internal pad are provided on the bottom wall of the nitrogen filling cavity, and the MEMS chip is electrically connected to the internal pad; an outer pad mounting area for welding an external pad and a circuit for passing a circuit connecting the internal pad and the external pad are provided on the bottom wall of the ceramic box body A through hole; a heat dissipation cavity is provided in the side wall of the ceramic box body, and a heat dissipation port and a plurality of heat conduction ports are respectively provided on the heat dissipation cavity, which are communicated with the outside and the nitrogen filling cavity respectively, and the plurality of heat conduction ports are arranged in sequence from bottom to top along the side wall of the nitrogen filling cavity, and a metal heat dissipation plate capable of closing the heat dissipation port is embedded in the heat dissipation cavity; an elastic heat sink is provided on the metal cover plate, and a heat conduction block for extending into the heat conduction port is provided on the elastic heat sink, and a thermal expansion and contraction part for connecting and disconnecting with the metal heat dissipation plate is provided on the heat conduction block, and the connection and disconnection spacing between the thermal expansion and contraction part of the heat conduction block and the metal heat dissipation plate increases step by step from bottom to top.

[0005] Preferably, the heat conduction opening is a strip-shaped opening arranged laterally.

[0006] Preferably, the heat conducting block is a bar-shaped block.

[0007] Preferably, a first expansion space is reserved between the strip block and the strip opening.

[0008] Preferably, the metal heat dissipation plate comprises a first rectangular heat dissipation portion and a second rectangular heat dissipation portion capable of covering the heat dissipation opening, the first rectangular heat dissipation portion is located in the heat dissipation cavity, and the second rectangular heat dissipation portion is located in the heat dissipation opening.

[0009] Preferably, a second expansion space is reserved between the top of the second rectangular heat dissipation portion and the heat dissipation cavity, a third expansion space is reserved between a side of the second rectangular heat dissipation portion facing the heat conduction port and the heat dissipation cavity, a compression spring for compressing the heat conduction block is provided in the second expansion space and the third expansion space, and a fourth expansion space is reserved between the first rectangular heat dissipation portion and the heat dissipation port.

[0010] Preferably, the metal heat sink, the elastic heat sink and the heat conducting block are all made of copper.

[0011] Preferably, the ceramic box body is made of silicon nitride material.

[0012] Preferably, the metal cover plate is welded or glued to the ceramic box body.

[0013] Preferably, the MEMS chip is welded or glued to the chip mounting area.

[0014] Compared with the prior art, the present invention has achieved the following technical effects:

[0015] 1. In the MEMS chip packaging structure of the present invention, when the heat dissipation of the metal cover plate cannot meet the heat generated by the MEMS chip, as the temperature rises, the elastic heat sink on the metal cover plate will transfer the heat to the heat conductive block. The heat conductive block expands due to the heat, and the bottom heat conductive block will first contact the metal heat sink, and then dissipate the heat through the metal heat sink, thereby increasing the heat dissipation area of ​​the MEMS chip packaging structure and improving the heat dissipation effect. If the heat dissipation demand is still not met, as the temperature continues to rise, the heat conductive blocks from bottom to top will contact the metal heat sink in turn as the temperature rises, until a certain heat conductive block contacts and meets the heat dissipation demand, or the top heat conductive block contacts the metal heat sink to achieve the maximum heat dissipation effect, thereby achieving a controllable heat dissipation.

[0016] 2. Expansion space is reserved between the heat conduction block and the heat conduction port in the present invention, and expansion space is reserved between the metal heat dissipation plate and the heat dissipation port and the heat dissipation cavity, which can prevent the heat conduction block and the metal heat dissipation plate from expanding and cracking the ceramic box body due to heat.

[0017] 3. The ceramic box body in the present invention is made of silicon nitride material. Since the MEMS chip is mainly composed of silicon, the expansion coefficient of the silicon nitride material is similar to that of the MEMS chip, thereby being able to avoid relative deformation that would damage the function of the MEMS chip. The MEMS chip is specifically a MEMS pressure sensor, a MEMS acceleration sensor, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0019] Figure 1 A cross-sectional view of a MEMS chip packaging structure provided with a type I metal heat sink;

[0020] Figure 2 A cross-sectional view of a MEMS chip packaging structure without a metal heat sink;

[0021] Figure 3 It is a longitudinal cross-sectional view of the MEMS chip packaging structure;

[0022] Figure 4 is a front view of a metal cover;

[0023] Figure 5 is a side view of a metal cover;

[0024] Figure 6 is an enlarged cross-sectional view of a heat dissipation cavity provided with a type I metal heat dissipation plate;

[0025] Figure 7 A cross-sectional view of a MEMS chip packaging structure provided with a type II metal heat sink;

[0026] Figure 8 It is an enlarged cross-sectional view of the heat dissipation cavity provided with a type II metal heat dissipation plate.

[0027] Explanation of the accompanying drawings: 1. Ceramic box body; 2. Metal cover plate; 3. MEMS chip; 4. Internal solder pad; 5. External solder pad; 6. First circuit; 7. Mounting port; 8. Nitrogen filling cavity; 9. Heat dissipation cavity; 10. Heat dissipation port; 11. Heat conduction port; 12. Metal heat sink; 13. Elastic heat sink; 14. Heat conduction block; 15. Second circuit; 16. On-off spacing; 17. First expansion space; 18. Second expansion space; 19. Third expansion space; 20. Fourth expansion space; 21. Compression spring. DETAILED DESCRIPTION

[0028] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0029] This embodiment provides a MEMS chip packaging structure, such as Figures 1 to 8As shown, it includes a ceramic box body 1 and a metal cover plate 2. The top of the ceramic box body 1 is provided with a mounting port 7. The metal cover plate 2 is used to block the mounting port 7. The metal cover plate 2 can be welded or glued to the top of the ceramic box body 1. A nitrogen filling cavity 8 is provided in the ceramic box body 1. The nitrogen filling cavity 8 is communicated with the mounting port 7. The bottom wall of the nitrogen filling cavity 8 is provided with a chip mounting area and a pad inner mounting area. The chip mounting area is used for the installation and fixation of the MEMS chip 3. The pad inner mounting area is used for the installation and fixation of the internal pad 4. The MEMS chip 3 and the internal pad 4 are connected through a first circuit 6. After the metal cover plate 2 closes the nitrogen filling cavity 8, the nitrogen filling cavity 8 is filled with nitrogen to prevent the impurities from affecting the circuit of the MEMS chip 3. The bottom wall of the ceramic box body 1 is provided with a pad outer mounting area and a circuit through hole. The pad outer mounting area is used for the installation and fixation of the external pad 5. The circuit through hole is penetrated with a second circuit 15 for connecting the internal pad 4 and the external pad 5. A heat dissipation cavity 9 is provided in the side wall of the ceramic box body 1, and a heat dissipation port 10 and a plurality of heat conduction ports 11 are provided on the heat dissipation cavity 9, which are respectively communicated with the outside and the nitrogen filling cavity 8. The plurality of heat conduction ports 11 are arranged in sequence from bottom to top along the side wall of the nitrogen filling cavity 8, and a metal heat dissipation plate 12 capable of closing the heat dissipation port 10 is embedded in the heat dissipation cavity 9. An elastic heat sink 13 is provided on the bottom wall of the metal cover plate 2, and a heat conduction block 14 is provided on the elastic heat sink 13. The number of the heat conduction blocks 14 is consistent with the number of the heat conduction ports 11, and the number of the heat conduction ports 11 is at least two. When the metal cover plate 2 is installed on the top of the ceramic box body 1, the elastic heat sink 13 extends into the nitrogen filling cavity 8, and the heat conduction block 14 is inserted into the corresponding heat conduction port 11. The heat conduction block 14 is provided with a thermal expansion and contraction part for connecting and disconnecting with the metal heat dissipation plate 12, and the on-off spacing 16 between the thermal expansion and contraction part of the heat conduction block 14 and the metal heat dissipation plate 12 increases step by step from bottom to top.

[0030] Working principle:

[0031] When the MEMS chip 3 is just started, the temperature inside the nitrogen filling cavity 8 is relatively low, and there is an on-off distance 16 between the thermal expansion and contraction part of the heat conductive block 14 and the metal heat sink 12. At this time, part of the temperature inside the nitrogen filling cavity 8 will be dissipated outwards through the metal cover plate 2 and the ceramic box body 1, and part will enter the nitrogen filling cavity 8 through the heat conductive port 11 and be discharged through the metal heat sink 12 and the heat dissipation port 10. As the temperature inside the nitrogen-filled chamber 8 gradually increases, it is difficult to dissipate heat in time by the above-mentioned heat dissipation method alone. The increased temperature will cause the thermal expansion and contraction parts of the heat-conducting block 14 to expand due to the heat. At this time, the thermal expansion and contraction parts of the heat-conducting block 14 located at the bottom will first fit with the metal heat sink 12, thereby connecting the metal heat sink 12 and the elastic heat sink 13. The temperature inside the nitrogen-filled chamber 8 will be quickly transferred to the metal heat sink 12 through the elastic heat sink 13 and the heat-conducting block 14, and then discharged to increase the heat dissipation speed. If the temperature inside the nitrogen-filled chamber 8 is still increasing, the thermal expansion and contraction parts of the heat-conducting block 14 from bottom to top will further expand as the temperature increases, and then the thermal expansion and contraction parts from bottom to top will gradually fit with the metal heat sink 12, increasing the connection area between the metal heat sink 12 and the elastic heat sink 13, thereby further increasing the heat dissipation speed. When the heat drops, the thermal expansion and contraction parts will shrink as the temperature drops, and then the thermal expansion and contraction parts from top to bottom will be separated and disconnected from the metal heat sink 12 in sequence.

[0032] In this embodiment, Figures 1 to 8 As shown, the heat conduction port 11 is a strip-shaped port arranged horizontally to increase the heat dissipation area. Heat conduction ports 11 are arranged on at least two side walls of the nitrogen filling cavity 8, and at least two strip-shaped ports are arranged vertically on the side wall with the heat conduction port 11. Figure 3 , the ceramic box body 1 has heat-conducting ports 11 on both short-side side walls of the nitrogen-filled cavity 8, and there are three heat-conducting ports 11, which are arranged up and down, and the corresponding metal cover plate 2 is provided with two elastic heat sinks 13, and each elastic heat sink 13 is provided with three heat-conducting blocks 14. After the metal cover plate 2 is installed on the installation port 7, the heat-conducting blocks 14 on the elastic heat sink 13 will be inserted into the three heat-conducting ports 11 accordingly. As the temperature rises, the heat-conducting blocks 14 expand due to the heat. Since the distance between the heat-conducting blocks 14 and the metal heat sink 12 is the smallest, they will first contact the metal heat sink 12. If the heat dissipation effect is not good, as the temperature rises, the heat-conducting blocks 14 in the middle will contact the metal heat sink 12, and finally the heat-conducting blocks 14 at the top will contact the metal heat sink 12 to dissipate heat.

[0033] Further, in this embodiment, Figures 1 to 8 As shown, the heat conducting block 14 is a strip-shaped block, which matches the strip shape of the heat conducting port 11 .

[0034] Further, in this embodiment, Figures 1 to 8As shown, a first expansion space 17 is reserved between the strip block and the strip opening, that is, the heat conductive block 14 is smaller than the heat conductive opening 11 in length and width, so as to provide expansion space for the heat conductive block 14 and prevent the heat conductive block 14 from expanding and cracking the side wall of the ceramic box body 1 at the heat conductive opening 11.

[0035] In this embodiment, Figures 1 to 8 As shown, the metal heat dissipation plate 12 includes a first rectangular heat dissipation portion and a second rectangular heat dissipation portion, the first rectangular heat dissipation portion is located in the heat dissipation port 10, the second rectangular heat dissipation portion is located in the heat dissipation cavity 9, and the second rectangular heat dissipation portion can cover the heat dissipation port 10. Further, in this embodiment, as Figures 1 to 8 As shown, there are currently two ways to set the metal heat sink 12. The first is: the first rectangular heat sink just fills the heat sink 10, and the second rectangular heat sink can just fill the heat sink cavity 9 to ensure the sealing of the nitrogen filling cavity 8 and prevent the nitrogen in the nitrogen filling cavity 8 from leaking from the heat sink cavity 9 and the heat sink 10. The second: a second expansion space 18 is left between the top of the second rectangular heat sink and the heat sink 9, and a third expansion space 19 is left between the side of the second rectangular heat sink facing the heat conduction port 11 and the heat sink 9. A vertically arranged compression spring 21 is provided in the second expansion space 18 to press the second rectangular heat sink against the bottom wall of the heat sink cavity 9. A horizontally arranged compression spring 21 is provided in the third expansion space 19 to press the second rectangular heat sink against the heat sink 10 and close the heat sink 10, ensuring that the nitrogen in the nitrogen filling cavity 8 will not leak out of the heat sink 10 from the heat sink 9, and at the same time ensuring that after the metal heat sink 12 is heated and expanded, the expansion of the second rectangular heat sink will not squeeze the heat sink 9. A fourth expansion space 20 is reserved between the corresponding first rectangular heat dissipation portion and the heat dissipation opening 10 , and the reserved expansion space ensures that the first rectangular heat dissipation portion will not squeeze and crack the heat dissipation opening 10 .

[0036] Further, in this embodiment, if Figures 1 to 8 As shown, the metal heat sink 12, the elastic heat sink 13 and the heat conducting block 14 are all made of copper, which has the best heat dissipation effect and a low thermal expansion coefficient.

[0037] In this embodiment, Figures 1 to 8 As shown, the ceramic box body 1 is made of silicon nitride material, and the thermal expansion coefficient of silicon nitride material is similar to that of the MEMS chip 3, thereby preventing the relative deformation of the two due to heat, which may damage the function of the MEMS chip 3.

[0038] In this embodiment, Figures 1 to 8 As shown, the metal cover plate 2 is welded or glued to the ceramic box body 1. The metal cover plate 2 can be fixed to the ceramic box body 1 by brazing or eutectic welding.

[0039] In this embodiment, Figures 1 to 8As shown, the MEMS chip 3 is welded or glued to the chip mounting area.

[0040] Further, in this embodiment, if Figures 1 to 8 As shown, during welding, a metal nickel layer and a gold layer can be provided in the welding area of ​​the ceramic box body 1 so that welding can be achieved at this position.

[0041] The present invention uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only used to help understand the method and core ideas of the present invention. At the same time, for those skilled in the art, according to the ideas of the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A MEMS chip packaging structure, characterized in that: The invention comprises a ceramic box body with a mounting opening on the top and a metal cover plate for blocking the mounting opening; a nitrogen filling cavity communicating with the mounting opening is provided in the ceramic box body, a chip mounting area for fixing the MEMS chip and an inner pad mounting area for welding an internal pad are provided on the bottom wall of the nitrogen filling cavity, and the MEMS chip is electrically connected to the internal pad; an outer pad mounting area for welding an external pad and a circuit through hole for passing a circuit connecting the internal pad and the external pad are provided on the bottom wall of the ceramic box body; a heat dissipation cavity is provided in the side wall of the ceramic box body The heat dissipation cavity is provided with a heat dissipation port and a plurality of heat conduction ports which are respectively communicated with the outside and the nitrogen filling cavity, and the plurality of heat conduction ports are arranged in sequence from bottom to top along the side wall of the nitrogen filling cavity, and a metal heat dissipation plate capable of closing the heat dissipation port is embedded in the heat dissipation cavity; an elastic heat sink is provided on the metal cover plate, and a heat conduction block for extending into the heat conduction port is provided on the elastic heat sink, and a thermal expansion and contraction portion for connecting and disconnecting with the metal heat dissipation plate is provided on the heat conduction block, and the connection and disconnection spacing between the thermal expansion and contraction portion of the heat conduction block and the metal heat dissipation plate increases step by step from bottom to top.

2. A MEMS chip packaging structure according to claim 1, characterized in that: The heat conduction opening is a strip-shaped opening arranged horizontally.

3. A MEMS chip packaging structure according to claim 2, characterized in that: The heat conducting block is a strip-shaped block.

4. A MEMS chip packaging structure according to claim 3, characterized in that: A first expansion space is reserved between the strip block and the strip opening.

5. A MEMS chip packaging structure according to claim 4, characterized in that: The metal heat dissipation plate includes a first rectangular heat dissipation portion and a second rectangular heat dissipation portion capable of covering the heat dissipation opening, the first rectangular heat dissipation portion is located in the heat dissipation cavity, and the second rectangular heat dissipation portion is located in the heat dissipation opening.

6. A MEMS chip packaging structure according to claim 5, characterized in that: A second expansion space is reserved between the top of the second rectangular heat dissipation portion and the heat dissipation cavity, a third expansion space is reserved between a side of the second rectangular heat dissipation portion facing the heat conduction port and the heat dissipation cavity, a compression spring for compressing the heat conduction block is provided in the second expansion space and the third expansion space, and a fourth expansion space is reserved between the first rectangular heat dissipation portion and the heat dissipation port.

7. The MEMS chip packaging structure according to claim 1, characterized in that: The metal heat sink, the elastic heat sink and the heat conducting block are all made of copper.

8. The MEMS chip packaging structure according to claim 1, characterized in that: The ceramic box body is made of silicon nitride material.

9. The MEMS chip packaging structure according to claim 1, characterized in that: The metal cover plate is welded or glued to the ceramic box body.

10. A MEMS chip packaging structure according to claim 9, characterized in that: The MEMS chip is welded or glued to the chip mounting area.

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